Comb growth varies with each individual bird. I too have personal experience with Silkies, I raise/breed them. After awhile of raising them, sexing them doesn't become that difficult.
Comb shape, isn't reliable either. Many of my U shaped combed chicks turned out female, combs stayed flat, or slightly bumpy. Posture, & behavior aren't great indicators all the time, you can get females that are more dominant, & have males that are more skittish/submissive.
Comb shape, & size...